Digester unit



Nv. l2, 1946. J. .1. DE LA RozA, sRr 2,410964 DIGESTER UNIT Filed March 29, 1944 TTOENEX In... -H/ 11111 i IIIILIIIII. .Il

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Patented Nov. 12, 1946 UNITED STATES PATT OFFICE DIGESTER UNI'BII Joaquin J. de la Roza, Sr., New York, N. Y.

Application March 29, 1944, Serial No. 528,537

2 Claims. i

This invention relates to improvements in a digester unit and refers more particularly to an assembly consisting ci an inner rotatable digestion vessel supported within an outer stationary vessel, the inner vessel having an inlet opening for introduction of the material to be treated and an outlet for discharge of the stock after digestion. In the annular space between the inner and outer vessels is circulated a heating medium for accurately controlling the temperature within the inner vessel.

Between the vessels at their ends are seals which prevent communication between the contents of the inner vessel and the jacket and automatically compensate for differences in elcnga tion caused by uneven heating.

The novelty resides primarily in providing a tubular screw conveyor digester in one section and grinding means in a separate section of the same vessel or in a separate vessel for mechanically redu'cing the material undergoing`digestion.

The digester unit is particularly adapted for digestion of iibrous substances in the presence of chemicals at elevated temperatures for the production oi uniformly high grade cellulose pulps.

The digester oiers 'facilities for uniformly treating fibrous material for a longer period of time in a continuous operation, utilizing a'much shorter vessel than is necessary for the same results when a tubular screw conveyor or mechanical reduction is not employed.`

There is provided in a single vessel means for digesting fibrous substances in the presence of chemicals at high temperature and simultaneously mechanically reducing the bundles of ber.

A further advantage of the design is the :fastening of the conveyor screw to the internal wall of the digesting vessel, thereby eliminating the objectional eect of a rotating screw which scrapes and damages the bre.

'in addition, the digestion unit combines facilities for more uniformly and effectively impregnating the fibrous material with chemical liquor while mechanically breaking up the brous bundles and disseminate more eiectively and separate the incrustations from the ber.

The digester unit eliminates to a great extent by-passing of undigested portions of the material undergoing treatment and substantially` preventing insucient or inadequate treatment of portions of the digesting mass, thereby increasing uniformity of the product.

it eliminates irregularities in the product produced by stopping and starting of the digester, a

, practice which normally seriously aiects the homogeneity of the mass; the action of the tubular screw conveyor preventing migration of the material longitudinally of the chamber.

In the accompanying drawing which forms a part of the instant specication, and is to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views,

Fig. 1 is a sectional side view of a digester in which the chemicaltreating and mechanical reduction sections are combined in a single vessel;

Fig. 2 is a fragmentary view oi a two-vessel unit in which the mechanical reduction is performed in a separate vessel.

Referring first to the digestion unit shown in Fig. l, an outer stationary cylindrical vessel lilv is supported upon foundations li means of supports i2. At the ends of the vessel i@ are flanges i3 to which are bolted covers iti and i5. An opening it in cover it serves as an inlet for material charged through pipe il'. In cover it is an opening i8 through which the material is discharged after digestion. A discharge pipe i9 is bolted to the opening.

Within the stationary vessel le is a concentric cylindrical vessel of smaller diameter 29 which has a common axis with the outer vessel. The inner vessel which encloses the digestion space is rotatable within the outer stationary vessel. The inner vessel is supported upon sets ci anged rollers 2i supported Within the outer stationary vessel. Pairs of the rollers are oiset somewhat from the low point of the inner digestion vessel and are hanged to roll upon traclss or rings 22 which surround the periphery or" the vessel at its ends and at necessary intervals along' its length where the vessel needs support.

As a source of power for rotating the inner vessel there is shown a motor 29 supported with its gear transmission upon a foundation 25. Upon the shaft of the motor is mounted a pinion 25 which meshes with a second pinion 2li on stub shaft 27. Gear E8 on the stub shaft meshes with a ring gear 29 surrounding and lxedly attached tothe shell of the inner vessel. Suitable stuing boxes surround shaft '2l' where it enters the auxiliary housing iii which surrounds gear 28 and communicates with the annular space between the two vessels. .a :duid medium circulated in the annular space is introduced through pipe 3i and is discharged through pipe 32. On the inner face of anges i3 are annularr rings 3S which form annular cylinders 34.

Reciprocatable in cylinders 3l are'seal rings 35 -whose inner ends contact the outer faces of flanges 20a of the inner rotating cylinder assuring a pressure-tight seal between the inner rotating vessel and the outer stationary vessel regardless of elongation differences of the respective vessels due to dierential heating. Pressure behind seal rings 35 for effecting the proper degree of contact between the rings and the' flange 20a is produced either by fluid pressure or by suitable compression springs, details of which form no part of the present invention.

The digestion space within the inner Vessel lis divided into sections by a perforated plate 38. Within the section to the left of this partition is shown the vanes of a, continuous screw 31. In the section to the right of partition 36 is a compartment equipped with a liner of material resistant to impacting elements shown diagrammatically at 39. 'Ihese impacting elements may be tubes, balls or rods or any type of objects which tumble about in the compartment and serve to break down or reduce mechanically the material undergoing digestion. A second perforated plate 4D prevents the impacting elements fromY escaping from the compartment but permits passage of the broken up fibrous material from the mechanical reduction compartment into the discharge pipe I8 of the dige'ster.

In the modified type of digester unit shown in Fig. 2 the single concentric vessels have been replaced by a pair of concentric vessels connected it is discharged through the perforations in plate 40 which are of a size which will permit ready passage of the treated mass, but prevents passage of the impacting elements. After passage through plate 40 the pulp is discharged through opening I8 and pipe I9. After leaving the digester the pulp mass may be treated in any desirable manner.

The operation with respect to the digester unit shown in Fig. 2 is similar to that shown in'Fig. 1

with the exception v that during the digesting period the mass passes through two separate digestion zones, onelimited to substantially chemical treatment and the other primarily to mechanical reduction. The two separate stages in Fig. 2 are joined by transfer pipe 4I.

gester of Fig. 2 'is diagrammatically shown -with many of the parts eliminated in the interest of simplicity as their details are more clearly shown and described in the single digester unit shown in Fig. 1. For controlling the temperature of digestion Y within the inner vessel -in both the single unit heating uids. Where refrigeration is desirable by a transfer pipe 4l. Instead of separating the inner vessel into two sections by the perforated plate 36, onedigester includes the section in which thev chemical treatment of the fibrous material is performed, the succeeding digesting vessel corresponds to the compartment for mechanically reducing the chemically treated mass identical in construction to the compartment to the right of the perforated partition in 36 in Fig. 1. By numbering corresponding parts of the digester Iunits shown in Figs. 1 and 2 with corresponding numerals best indicates the similarities between the structural elements. In Fig. 2 the outer stationary casing is shown at l0, the inner rotating vessel at 20. The supports and drying mechanism is, of course, identical. Attached to the inner wall .of the inner vessel is a continuous screw 31 which serves to advance the material as the vessel rotates.

Referring to the operation of the digester shown in Fig. 1 material to be digested is introduced through pipes I1 and inlet opening I6 in the cover l 4 of the stationary digester. This inlet lopening communicates with a chamber in the' inlet end of the stationary vessel which is in alignment with vthe open end of the inner rotating vessel. 'Rotation of the irmer vessel causes the material to be picked up by the nights 31 of the screw attached to the inner wall of the vessel advancing material slowly longitudinally of the vessel as it rotates. The digestion liquor is introduced to the material prior to its introduction.

As a result of the breaking down of the material resulting from the reaction of the digestion liquor and the mechanical effect of the tumbling as it advances through the vessel, on arrival atin the digestion ofany material a, brine may be circulated or other type of refrigerant may be circulated through the annular jacket.

While the digester unit has been described in.

grated and the temperatures of digestion acc curately maintained.

It is contemplated also that inthe treatment of fibrous substances there may be interposed between the'mechanical and ,chemical stages as shown in Fig. 2, a deliquefying treatment as by pressing vor rolling.-

while'in has been proved preferable to menne slightly the digesters so that drainage will readily e take place, it is a feature of the digester'units that they need not be placed at any appreciable slant or inclination in order to produce the desired forward movement or advancement of the digesting mass as this is taken care of'by the effect of screw 31. The screw flights also have'the effect of uniformly mixing the mass with thetreating liquor. By ,attaching the internal screw io`the wall of the inner vessel, the objectionable effectlof a' rotating screw which'scrapes and damages fiberV is avoided.

From lche foregoing it win be seenztht the mvention is one Well adapted to attainall of thel ends and objects herein set forth together with other advantageswhich areobvioual and which are inherent to thestructure.

As many possible embodiments `may 4be made The details of both the chemical digester and mechanical diculating a fluid medium in the annular space between the Vessels, the former of said vessels enclosing a digestion space, a perforated partition dividing the digestion space into separate sections, said perforated partition adapted for passing digested material therethrough, an open screw aixed to the inner wall of one section for advancing material, impacting objects Within the other section of the digestion space, and inlet and discharge pipes at opposite ends of the digestion space.

2. A digester unit comprising substantially horizontal concentric cylindrical vessels having a common axis and a sealed annular space therebetween, means for circulating a. fluid medium through the annular space, the inner vessel rotatable within the outer stationary vessel, said inner 

